The water intoxication, or hypoatremia I think, is mostly overhyped. People think that if they drink more than half a gallon of water during a normal day they'll get it, and that's just wrong. The people getting that are extreme cases, an insane amount of water in a short period of time. Combine that with sweating alot, and it's even worse, because what's happening is that you're diluting your electrolytes, and sweating speeds up that process.
However, personally I think I have drank too much water and may be paying for it. Several months ago I posted some health problems of mine, couldn't figure out for anything. It was mainly severe fatigue after eating, and I'm not kidding when I say "severe". I'm not talking about getting a little sleepy when you've eaten too much. My testosterone bottomed out too. After countless hours of experimentation and countless more lectures from people who say I had diabetes, I recently found out that I can make these symptoms occur with nothing but tap water. I can reproduce it. All I have to do is drink a glass of water. That's it. 8 ounces of water and my head will be swimming, I need to take a nap, etc. Smaller amounts like 4 ounces often make me feel funny but 8 ounces will make me feel like hell. Some bottled water doesn't affect me though. I can reproduce it any time of the day, even first thing in the morning and after biking alot, when I know I'm dehydrated and not water logged from drinking 4-8 ounces. I can reproduce it on an empty stomach, or after a big meal, all I have to do is drink a glass of water while I'm eating.
After researching this more, I found that some people have a sensitivity to certain chemicals in tap water, especially fluoride. Even if you're not sensitive to it, you can overload your system with it and effectively get fluoride poisoning. After that happens, you will get the same symptoms I've been complaining about, and often many others. Fluoride can decrease your testosterone too.
Starting a few months before I got sick, I bumped up my water consumption alot. I would drink at least a gallon a day, which is still alot less than some people. When I'd exercise I'd often hit 1.5 gallons. Never thought much about it until now. I think it was the tap water. Some bottled water doesn't affect me much, if at all, but I've noticed all of them were filtered by reverse osmosis. I have a good particle filter at home, but it's not reverse osmosis. This type of filter is the only one that will take out fluoride as far as I know.
Anyway, not to scare anybody, but, I've been sick for 8 months now, it ruined my year, and if I can reproduce these sick feelings with a fairly small amount of tap water, I figured maybe I should mention it. I know it sounds crazy, but here in the last two weeks I have severely limited my water consumption, especially filtered tap water, and I have felt alot better, any fatigue episode has been very minor. My testosterone has also been increasing. When I first figured it out, it jumped up about 35 points in less than a week. That was a few weeks ago and I haven't been tested again, but it's pretty obvious that it's even higher.